Description: Comedonal openings, crypts and bluish pigment in keratinocytes in this thick seborrhoeic keratosis.

History: The thicker dark seborrhoeic keratosis will often have a bluish tinge to it under the dermatoscope presumably because of the depth of melanin pigment in a thick lesion. All this pigment is in epidermal cells whereas we usually associate the colour blue with melanin pigment or nests deep in the dermis of melanocytic lesions.